Plane stress detection device and detection method

The invention provides a plane stress detection device and method, and the device comprises a pedestal which is provided with a circular installation part penetrating through the pedestal, and the periphery of the installation part is provided with an angle dial; the angle adjusting device is mounted in the mounting part and can rotate relative to the base, and the angle adjusting device comprises a body and an angle adjusting part; the body is provided with a first side facing the surface of an object to be detected, a second side back to the object to be detected, opposite arc-shaped surfaces connected with the first side and the second side and matched with the circular inner wall of the mounting part in shape, and side surfaces adjacent to the arc-shaped surfaces; an ultrasonic transmitting probe mounting concave part and an ultrasonic receiving probe mounting concave part which are symmetrical relative to the circle center of the mounting part are arranged on the second side; a first transducer cavity an